Yet another Mourning Warbler today. This one was in the southwestern alcove. I don’t know if it had been chasing this grasshopper and they both died at the window, but it sure did look unusual to find these two together.
As storms rolled through overnight, I assumed I might find a casualty this morning. There were two: a completely rain-soaked female Indigo Bunting in the southwestern alcove and a completely dry and fluffy Mourning Warbler at the south entrance under the rain protection provided by the portico’s overhanging roof. The latter was an AHY male with fat = 3.
This morning I found the fifth dead Mourning Warbler on campus in the past two weeks: Four (including this one on the northwest alcove) at the Noble Research Center and one incidental find just across a small parking lot from the NRC at the Food and Agricultural Products Center.
For a bit of perspective on how unusual this is, i.e., Mourning Warbler is a secretive, migratory transient in Central Oklahoma that is far more likely to be found dead at a window than live on an eBird checklist, this was the 15th Mourning Warbler casualty I’ve found at the NRC since I began surveys in August of 2009. In comparison, I’ve only found 17 casualties over the same time period of the far more abundant and year ’round resident Mourning Dove.
This one was a hatch-year bird – so just a month or two old – with fat = 1.
There was more mourning for me this morning, as I found a nearly identical bird to the casualty from Tuesday: Hatch-year Mourning Warbler; indeterminate sex; fat = 3. Here is another youngster on its first journey from the boreal forest to perhaps Colombia or Ecuador, cut down in perfect health from a stupid window in the southwest alcove.
Well, here we go. Today marks the end of my 9th year conducting spring/summer monitoring for window-killed birds at the Noble Research Center. Tomorrow I begin year 10. Ten years of near daily monitoring of window-killed birds. Here’s a quick 9-year wrap-up:
- 40: average minimum casualties annually
- 360: total casualties (minimum)
- 64: species confirmed as fatalities
- 10: average number of days for birds to be removed/scavenged
Top ten (eleven) species most commonly encountered as casualties at this site:
- Lincoln’s Sparrow (45)
- Ruby-throated Hummingbird (29)
- Painted Bunting (24)
- Indigo Bunting (20) *tie* Grasshopper Sparrow (20)
- Mourning Dove (17)
- Clay-colored Sparrow (16)
- Nashville Warbler (14)
- Common Yellowthroat (11) *tie* Mourning Warbler (11) *tie* Song Sparrow (11)
I’m mourning the loss of another one today – this AHY female I found at the northwest alcove. She was fat (=3) and healthy at 12.5g.
This was the unofficial 315th casualty on the project and, for a new sobering record, the 44th this year. The previous annual high was 41. We’ve surpassed that already in 2017 and, for us, migration is really just ramping up.
On the heels of an impressive southbound flight last night,
. . . I found two casualties this morning.
There was a HY Chipping Sparrow in the northwest alcove. The bird had evidently been stepped on or perhaps run over by a maintenance vehicle. I left it in place for a removal trial.
Also, near the main north entrance (actually at a west-facing facade in the corner) was a Mourning Warbler. The bold eyering and long undertail coverts looked tantalyzingly like a Connecticut Warbler. It was, however, an AHY-U Mourning Warbler. The bird was 13.5g and bulging with fat (3).
This was the 10th Mourning Warbler on the project.
With apologies for the 1) poor and 2) non-existent photos . . .
I found an ASY male Mourning Warbler (fat = 0) at the main north entrance this morning. He was waaaaay better looking than these photos attest, and I bet he was even more handsome in life.
In the northwest alcove lay a female (with well-developed brood patch!) Yellow-billed Cuckoo (no photo). I left the cuckoo in place, as the ants were already doing a number on her.
In scavenging news, the starling from 5/18 was both moved and eaten: I found a remnant pile of its larger feathers about 5m away from the bird’s location. Whatever picked it up had taken it south to the bushes in front of the northern entrance.
I found this AHY, fat = 2, female Mourning Warbler at the southwest alcove this morning. My warm memories of these birds are of finding them skulking through the ferns in Pennsylvania’s Allegheny National Forest, with the males’ ringing and rolling song sharing airspace with the Winter Wrens’. Dead at a window in a landscape of steel, glass, and concrete is an ill-fitting end to what must have been an exciting, adventurous life for this little gem.
No casualties at the Noble Research Center this morning, but I found this bonus Mourning Warbler on the south side of the Food and Ag Products Center.
This was a hatch year bird, and probably a female. She was in prime shape for migration, with fat = 2. No Mourning Warbler should end up stiff on a sidewalk in Oklahoma. Here’s where these birds are supposed to be in the first two days of September:
Today, the Painted Bunting remains in place but the Ruby-throated Hummingbird carcass is fully gone. It lasted approximately 5 days.
At the north entrance, I flushed a small, olive-green warbler with noticeably long and yellow undertail coverts. The bird bumped the glass near me, but I was able to steer it away from the building and into some ornamental trees. I was unsuccessful at relocating it after that. My best guess is that the bird is a Mourning Warbler, given size, coloration, and the long undertail coverts. The spatial distribution of collisions now looks like this:
Here is just a quick summary of casualties at the Noble Research Center from July through December 2010:
I detected 25 individuals of at least 16 species among the casualties. The complete list:
grasshopper sparrow – 4
ruby-throated hummingbird – 2
mourning warbler – 2
song sparrow – 2
Lincoln’s sparrow – 2
unidentified passerine (1 warbler, 1 sparrow) – 2
black-and-white warbler – 1
Carolina wren – 1
mourning dove (juv) – 1
least flycatcher – 1
common yellowthroat – 1
black-throated green warbler – 1
brown thrasher – 1
house wren – 1
red-breasted nuthatch – 1
white-throated sparrow – 1
field sparrow – 1
Because I was able to get to the NRC earlier each day during autumn than practical in 2009, I encountered more individuals that were stunned and “trapped” by the building for some time period without obvious mortal injury. Most of these birds are presumed to have eventually moved on, but it is quite likely that the house wren and one of the Lincoln’s sparrows on the “stunned” list were unsuccessful in their respective bids to escape from the confusion of the NRC, and are listed above. The bat represents the first mammalian “capture” by the NRC:
Lincoln’s sparrow – 5 (4 in one flock)
house wren – 1
common yellowthroat – 1
Nashville warbler – 1
grasshopper sparrow – 1
dark-eyed junco – 1
It’s dark when migrants like this Lincoln’s sparrow drop out of the sky and try to find a good spot in which to rest for the day. I’m beginning to think that most collisions are occurring in that last hour before sunrise.
I noticed this poor junco yesterday morning (11/8). It’s just a few feet from this Mourning Warbler that hit the same window on May 17, and this Sharp-shinned Hawk that hit that same window on Oct. 16, 2009. So the same window has now claimed at least three individuals of three different species in a little more than a year. If you look out from the north window on the 2nd floor of Ag Hall, you can see the junco and the mummified remains of the Mourning Warbler.
It looks like Sep. 1 is the only day I did not check for casualties this month. Here’s what I found on the days I did check:
2 Mourning Warblers
1 unidentified warbler
1 Least Flycatcher
1 Common Yellowthroat
1 Black-throated Green Warbler
1 Ruby-throated Hummingbird
1 Brown Thrasher
Yet another Mourning Warbler has met its end on one of the west alcoves of the Noble Research Center. This one is a hatch year bird of undetermined sex (though the faint orangey wash to the yellow on the upper breast has me thinking it’s a male). This bird was also in prime condition for migration: fat score = 3.
I can’t tell if the damage to its right foot was caused by one catastrophic bump against the glass or if this was one of the poor birds who struggled against the building for hours before exhausting itself. The latter scenario is unlikely given the amount of fat the bird still had.
I did find a trapped immature Mourning Warbler in one of the west side alcoves of the NRC. The bird was on the ground when I found it. It wasn’t panting, but did look tired. My disturbance cause it to flutter against the glass before turning around and heading back out the way it came in. It took 2 or 3 tries of me shooing it away from the building before it finally flew almost completely vertically up and out over the roofline.
It’s possible this bird would have survived on its own so I won’t count it as a casualty. But it certainly was vulnerable to predators, and it might have a tough time today finding a safe place to rest and refuel.
Last night (Thursday), our recent intense heat and humidity (108 heat index on Sep. 1) broke in a major way with a powerful gust front and storm system. A straight line wind speed of 87 mph was recorded in Oklahoma City. Overnight the temperature dropped considerably, and temperatures were in the upper 50s with a north breeze this morning. That weather seems to have finally brought down some migrants from the North.
I found two birds this morning, and both represented identification challenges. The first was an immature Mourning Warbler:
This bird’s throat was actually pretty grayish-white, rather than the obvious yellow one might expect on this species. Thus, I considered very carefully whether it might be a MacGillivray’s Warbler. But the broken eye-ring on this bird was barely broken, extending closer to the “corners” of the eye than typical for MacGillivray’s. Also, the undertail coverts extended very near to the tail tip, as expected for Mourning. Thus despeite the lack of a clear yellow throat, I’m confident calling this bird a Mourning Warbler.
I’m also confident in describing it as a fat score = 3. The bird’s fat completely filled the furcular hollow and extended over a large portion of the breast. The fat can be seen in the following photo right through the bird’s relatively transparent skin. The breast skin of a bird without a fat deposit would look sort of brick red in color, kind of like dark meat on a chicken. On this bird, the off-white color of subcutaneous fat is obvious:
The next bird was represented only by a few remiges:
These were smaller than the primaries on the Mourning Warbler, and rather dark gray with just a slight edge of olive green. The size, color, and lack of pattern indicate “warbler” to me, but it will have to be listed as “unknown.”
In this case, both birds hit the building after it stopped raining last night (~ 9 pm), judging from the excellent condition of the feathers. One was scavenged in that time – but still obvious to me – and one was untouched. The specimens were found about 7m from each other on the north side of the building.
On August 20th, I completed a full year of regular surveys for window-killed birds at the Noble Research Center. Here are some vital statistics for August 20 2009–August 20 2010:
I conducted (occasionally with help from assistants like Danielle Benson) 153 surveys over the full year of monitoring. This equates to an average of 2.39 days between surveys.
Coverage was irregular throughout the year. For example I did no monitoring in January 2010. For this reason, analysis of casualties by season must be viewed through the lens of dissimilarities in sampling effort among the seasons. I defined sampling effort as the number of surveys per days in a given season. I defined seasons as follows: Dec. 1–Mar. 20 (110 days) = “winter,” Mar. 21–May 20 (61 d) = “spring,” May 21–Aug. 19 (91 d) = “summer,” and Aug. 20–Nov. 30 (102 d) = “autumn.” The 11 winter surveys provided an effort of 0.10. This approximates 10 days on average between surveys. Effort indices were 0.87 for spring (53 surveys in 61 days), 0.44 for summer, and 0.48 for autumn. Thus effort was most consistent during spring with near daily surveys.
I recorded window strike mortality for 38 individuals of 22 different species over the year of monitoring. This rate of collision mortality places the NRC on par with other high-mortality buildings referenced in Klem 1990 and O’Connell 2001.
Of the 38 casualties, 5 were “local” (i.e., recently-fledged offspring of local breeders), 5 were “hatch year” birds (i.e., “immature”, or birds < 1 yr. old), and 28 were adults or of undetermined age.
Of the the 38 casualties, 8 were identifiable as male, 5 as female, and 25 were of undetermined sex.
As in O’Connell 2001, Neotropical migrants in passage comprised the greatest percentage of individuals among all casualties. The birds dying at the NRC are not local residents that commonly occur in the OSU campus. These are transient individuals traveling long distances that just happen to meet their end here. (Note that the number of resident individuals among the casualties is inflated by the fact that 5 of the 7 casualties were recently fledged mourning doves and northern cardinals.)
On at least four occasions, I encountered live birds that appeared to be trapped near a window but were not injured from a collision. These individuals are not included in the collision data, but they may have been had I not been there to flush them away from the windows and encourage them to move along:
9/22/09: Grasshopper Sparrow and suspected Swainson’s Thrush
10/19/09: Grasshopper Sparrow
11/2/09: Two Dark-eyed Juncos
6/21/10: Carolina Wren
The scavenging rate proved to be unpredictable over the year. For example, some carcasses left in place remained visible for several weeks and were untouched during that time. Others were identifiable only from feathers left behind of a carcass that, based on the timing of my most recent survey, had been scavenged just a few hours after the bird’s unfortunate collision. Further confounding the interpretation of scavenging rates, some carcasses were scavenged but readily identifiable feathers of the carcass were left behind and still in evidence long after scavenging. For example, the Yellow-billed Cuckoo that I found on 6 June 2010 was scavenged on 15 June. As of 3 September 2010, that bird’s primaries are still readily apparent at the location where I first found it on June 10th, approximately 86 days after the bird’s death.
I found evidence of 15 scavenged carcasses over the year. Thus, out of 38 total casualties, 39% were ultimately scavenged. (Of course, I collected the majority of the carcasses I found, most of which were fresh and in excellent condition and were photographed for entries in this blog. Presumably, a high percentage of these would ultimately have been scavenged.) Two carcasses were scavenged on day 0 and three were scavenged after just one day in situ. Four were in evidence for at least 30 days; the average number of days a carcass was apparent in place was 18.6 – nearly 8 times the length of time between consecutive surveys. Thus, the regular, frequent surveys provided ample opportunity to discover carcasses before they were removed or no longer visible. In addition, the most frequent condition of freshly scavenged carcasses of warbler-sized birds was a pile of remiges cleanly sheared off near the base of the feathers. Thus, even small birds were usually left in place after scavenging; this increased the probability that I would find the carcass even if it had been scavenged. Nonetheless, it is likely that at least some individuals were scavenged and removed from the site before I could document the casualty, so mortality rates calculated from my surveys must be viewed as underestimates of actual mortality.
The following table lists all the species found as window collision casualties at the Noble Research Center, 8/20 2009–8/20 2010:
Common Yellowthroat 5
Mourning Dove 5
Lincoln’s Sparrow 4
Black-and-White Warbler 3
Grasshopper Sparrow 3
Painted Bunting 2
Mourning Warbler 1
Gray Catbird 1
Wilson’s Warbler 1
Canada Warbler 1
Indigo Bunting 1
Orange-crowned Warbler 1
Song Sparrow 1
Nashville Warbler 1
Dark-eyed Junco 1
Sprague’s Pipit 1
Swainson’s Thrush 1
Orchard Oriole 1
Northern Cardinal 1
Yellow-billed Cuckoo 1
Ruby-throated Hummingbird 1
Carolina Wren 1
The same window that claimed a Sharp-shinned Hawk last fall today claimed a Mourning Warbler. Sad to see a little bird like this on such a long journey lose its life in such a weird place and under such pointless circumstance.
I have checked the Noble Research Center on the following dates (Aug. 20, 22, 25, 28, and Sep. 3) with the following results: no casualties yet. Today (Sep. 7), I found the first casualty of the 2009 season: a hatch year male Mourning Warbler (fat = 2).
The range map indicates migration through Oklahoma en route to wintering grounds in northern South America: